Ephesians 4:29 says to speak only what is helpful for doing what?

Answer: Building others up

Let no unwholesome talk come out of your mouths, but only what is helpful for building up the one in need.

“Let no unwholesome talk come out of your mouths, but only what is helpful for building up the one in need and bringing grace to those who listen.”— Ephesians 4:29 (BSB)